1. Technical Field
The present invention relates to a projection type image display apparatus, which displays a projection image on a screen, and a projection optical system which is used in the projection type image display apparatus.
2. Description of the Related Art
In recent years, projector apparatuses have been widely known as a projection type display apparatus that displays a projection image on the screen. In particular, recently, there has been an increase in the demand for ultra-wide-angle front projection type image display apparatuses capable of displaying an image on a large screen while reducing a projection space. When using the ultra-wide-angle front projection type image display apparatuses, it is possible to project a beam diagonally onto the screen, and thus it is also possible to project an image on a large screen in a limited space. On the other hand, since occurrence of aberrations caused by an increase in angle of view increases, the size of the optical system tends to increase.
There have been proposed projection type image display apparatuses that are miniaturized by employing a flat mirror. Specifically, there has been proposed an apparatus capable of suppressing the size of the projection optical system in the depth direction in a state where it is small in a way that two flat mirrors are disposed between the first optical system and the second optical system constituting the projection optical system (for example, refer to International Publication Pamphlet No. 06-043666). Further, one flat mirror may be disposed on the first optical system constituting the projection optical system and another one flat mirror may be disposed between the first optical system and the second optical system constituting the projection optical system. With such a configuration, there has been proposed an apparatus capable of achieving a decrease in size of the projection optical system (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-165202).